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                    <h1>AVFoundation学习笔记十 AVCaptureSession2</h1>
                    
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                            Posted by Cyrus on
                        
                        
                            2018-11-12
                        
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                <p>视频缩放<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br></pre></td><td class="code"><pre><span class="line">- (BOOL)cameraSupportsZoom &#123;</span><br><span class="line"> 	return self.activeCamera.activeFormat.videoMaxZoomFactor &gt; 1.0f;        // 1</span><br><span class="line">&#125;</span><br><span class="line">- (CGFloat)maxZoomFactor &#123;</span><br><span class="line"> 	return MIN(self.activeCamera.activeFormat.videoMaxZoomFactor, 4.0f);    // 2</span><br><span class="line">&#125;</span><br><span class="line">- (void)setZoomValue:(CGFloat)zoomValue &#123;                                   // 3</span><br><span class="line"> 	if (!self.activeCamera.isRampingVideoZoom) &#123;</span><br><span class="line">        NSError *error;</span><br><span class="line">        if ([self.activeCamera lockForConfiguration:&amp;error]) &#123;              // 4</span><br><span class="line">            // Provide linear feel to zoom slider</span><br><span class="line"> 			CGFloat zoomFactor = pow([self maxZoomFactor], zoomValue);      // 5</span><br><span class="line">            self.activeCamera.videoZoomFactor = zoomFactor;</span><br><span class="line">            [self.activeCamera unlockForConfiguration];                     // 6</span><br><span class="line"> 		&#125; else &#123;</span><br><span class="line">            [self.delegate deviceConfigurationFailedWithError:error];</span><br><span class="line">        &#125;</span><br><span class="line"> 	&#125;</span><br><span class="line">&#125;</span><br><span class="line">- (void)rampZoomToValue:(CGFloat)zoomValue &#123;                                // 1</span><br><span class="line">    CGFloat zoomFactor = pow([self maxZoomFactor], zoomValue);</span><br><span class="line"> 	NSError *error;</span><br><span class="line"> 	if ([self.activeCamera lockForConfiguration:&amp;error]) &#123;</span><br><span class="line"> 		[self.activeCamera rampToVideoZoomFactor:zoomFactor                 // 2</span><br><span class="line">                                        withRate:THZoomRate];</span><br><span class="line"> 		[self.activeCamera unlockForConfiguration];</span><br><span class="line"> 	&#125; else &#123;</span><br><span class="line"> 		[self.delegate deviceConfigurationFailedWithError:error];</span><br><span class="line"> 	&#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></p>
<p>人脸检测<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br></pre></td><td class="code"><pre><span class="line">- (BOOL)setupSessionOutputs:(NSError **)error &#123;</span><br><span class="line">//设置输出数据类型</span><br><span class="line">    self.metadataOutput = [[AVCaptureMetadataOutput alloc] init];           // 2</span><br><span class="line">    if ([self.captureSession canAddOutput:self.metadataOutput]) &#123;</span><br><span class="line">        [self.captureSession addOutput:self.metadataOutput];</span><br><span class="line">//设置人脸检测</span><br><span class="line">        NSArray *metadataObjectTypes = @[AVMetadataObjectTypeFace];         // 3</span><br><span class="line">        self.metadataOutput.metadataObjectTypes = metadataObjectTypes;</span><br><span class="line">        dispatch_queue_t mainQueue = dispatch_get_main_queue();</span><br><span class="line">        [self.metadataOutput setMetadataObjectsDelegate:self                // 4</span><br><span class="line">                                                  queue:mainQueue];</span><br><span class="line">        return YES;</span><br><span class="line">    &#125; else &#123;                                                                // 5</span><br><span class="line">        if (error) &#123;</span><br><span class="line">            NSDictionary *userInfo = @&#123;NSLocalizedDescriptionKey:</span><br><span class="line">                                           @&quot;Failed to still image output.&quot;&#125;;</span><br><span class="line">            *error = [NSError errorWithDomain:THCameraErrorDomain</span><br><span class="line">                                         code:THCameraErrorFailedToAddOutput</span><br><span class="line">                                     userInfo:userInfo];</span><br><span class="line">        &#125;</span><br><span class="line">        return NO;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line">//人脸检测回调</span><br><span class="line">- (void)captureOutput:(AVCaptureOutput *)captureOutput</span><br><span class="line">didOutputMetadataObjects:(NSArray *)metadataObjects</span><br><span class="line">       fromConnection:(AVCaptureConnection *)connection &#123;</span><br><span class="line">    for (AVMetadataFaceObject *face in metadataObjects) &#123;                   // 2</span><br><span class="line">        NSLog(@&quot;Face detected with ID: %li&quot;, (long)face.faceID);</span><br><span class="line">        NSLog(@&quot;Face bounds: %@&quot;, NSStringFromCGRect(face.bounds));</span><br><span class="line">    &#125;</span><br><span class="line">    [self.faceDetectionDelegate didDetectFaces:metadataObjects];            // 3</span><br><span class="line">    </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></p>
<p>条形码检测<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br></pre></td><td class="code"><pre><span class="line">- (BOOL)setupSessionOutputs:(NSError **)error &#123;</span><br><span class="line">    self.metadataOutput = [[AVCaptureMetadataOutput alloc] init];</span><br><span class="line">    if ([self.captureSession canAddOutput:self.metadataOutput]) &#123;</span><br><span class="line">        [self.captureSession addOutput:self.metadataOutput];</span><br><span class="line">        dispatch_queue_t mainQueue = dispatch_get_main_queue();</span><br><span class="line">        [self.metadataOutput setMetadataObjectsDelegate:self</span><br><span class="line">                                                  queue:mainQueue];</span><br><span class="line">        NSArray *types = @[AVMetadataObjectTypeQRCode,                      // 1</span><br><span class="line">                           AVMetadataObjectTypeAztecCode,</span><br><span class="line">                           AVMetadataObjectTypeUPCECode];</span><br><span class="line">        self.metadataOutput.metadataObjectTypes = types;</span><br><span class="line">    &#125; else &#123;</span><br><span class="line">        NSDictionary *userInfo = @&#123;NSLocalizedDescriptionKey:</span><br><span class="line">                                       @&quot;Failed to still image output.&quot;&#125;;</span><br><span class="line">        *error = [NSError errorWithDomain:THCameraErrorDomain</span><br><span class="line">                                     code:THCameraErrorFailedToAddOutput</span><br><span class="line">                                 userInfo:userInfo];</span><br><span class="line">        return NO;</span><br><span class="line">    &#125;</span><br><span class="line">    return YES;</span><br><span class="line">&#125;</span><br><span class="line">- (void)captureOutput:(AVCaptureOutput *)captureOutput</span><br><span class="line">didOutputMetadataObjects:(NSArray *)metadataObjects</span><br><span class="line">       fromConnection:(AVCaptureConnection *)connection &#123;</span><br><span class="line">    [self.codeDetectionDelegate didDetectCodes:metadataObjects];            // 2</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></p>


                
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